Are mercury levels in fishery products appropriate to ensure low risk to high fish-consumption populations?

The main goal of the present study is to determine the sources of methylmercury (MeHg) for high fish-consumption populations with the Portuguese population as showcase, as Portugal is the EU country with the highest fish consumption per capita (2019: 59.91 kg year^-1). Since limited information is available on the effective levels of mercury after culinary treatments, cooked and raw codfish (Gadus morhua), hake (Merluccius merluccius), octopus (Octopus vulgaris), horse mackerel (Trachurus trachurus) and sardine (Sardina pilchardus) were considered. The mercury concentration ranking Hake > Horse mackerel > Codfish > Octopus > Sardine was observed in all situations (cooked and raw samples) for both MeHg and total mercury (T-Hg). The gathered results reinforce the general assumption that the loss of moisture during cooking increases MeHg and T-Hg concentrations in fish, but the idea that MeHg in fish muscle tissue represents the bulk of T-Hg cannot be generalised, as our study determined a MeHg/T-Hg ratio of 0.43 for grilled sardines.